Certain polymeric compositions do not have sufficient heat resistance in order to allow their use as plastic articles, notably as vehicle parts. In particular, polymeric compositions used as materials in the automotive field, notably inside cars behind the glazed surfaces, should be able to withstand temperatures above 120° C.
Various methods have been described for improving heat resistance of polymers, notably incorporation of rigid functions into the polymer, for example aromatic rings. However, a large molar proportion of aromatic rings (of more than 25% molar) has to be incorporated into the polymer in order to observe an improvement in the heat resistance of the polymer, which is costly and which changes the behavior of the polymer: the crystallization kinetics become much lower. The polymer is amorphous in the injection process and its heat resistance is too low for making plastic articles, notably vehicle parts. Further because of the presence of these aromatic rings, the modified polymers cannot stem from renewable resources.
Poly(esteramide) polymers advantageously have interesting thermal, mechanical and biodegradability properties and are therefore materials suitable for preparing plastic articles which may withstand temperatures above 120° C. Methods for preparing these poly(esteramide) polymers by polymerization have been described in the literature.
However, it was observed that these methods only operate with certain monomers used as a starting product and not with other ones. In particular, attempts for obtaining poly(esteramide) polymers from glutaric and succinic acid (or from their derivatives, notably the corresponding anhydrides) have failed, since these polymers form highly stable cyclic imides preventing polymerization. For example, the method applied by Thomas Fey et al. (Polym. Int. 52, 1625-1632, 2003) does not operate with N-(hydroxyalkyl)imides obtained from succinic anhydride, as starting monomers. Also, Pieter J. Dijkstra (Macromol. Symp. 152, 127-137, 2000) reports an unsuccessful polymerization attempt from dimethyl 6,11-diaza-5,12-dioxo-1,16-hexadecanedioate, obtained from glutaric anhydride. Indeed, 6,11-diaza-5,12-dioxo-1,16-hexadecanedioate cyclizes and the product prevents polymerization and the formation of a poly(esteramide) polymer.
However, as glutaric and succinic acid monomers are inexpensive, polymers prepared from the latter would be of interest.